Citation: Sedej, I., Milczarek, R.R., Wang, S., Sheng, R., Avena Bustillos, R.D., Takeoka, G.R. 2014. Centrifugation as a pre-treatment in olive mill wastewater processing (abstract). Institute of Food Technologists Annual Meeting & Food Expo. Paper No. 120-01.
Technical Abstract: Olive mill wastewater (OMWW), generated during production of olive oil, is an untapped source of nutritious compounds. Thus, processors want to separate OMWW into a high-value, concentrated product stream and near-pure water. However, the amount and characteristics of the produced OMWW depend on the milling system (2-phase or 3-phase). Since centrifugation is already used in the production of olive oil, it could be economically utilized as a pre-treatment in OMWW processing. Thus, the objectives of this study were to evaluate efficiency of centrifugation and identify optimum centrifugation time and speed for 2-phase and 3-phase OMWW using industrially-feasible conditions. It was previously determined that the quality parameters of OMWW influenced by centrifugation are total solids (TS), dissolved solids (DS), suspended solids (SS), turbidity, and chemical oxygen demand (COD). A response surface experiment (full factorial central composite design) was conducted to establish the speed/time combinations necessary to minimize values for all measured quality parameters in the separated near-pure water stream. OMWW from two California mills (one 2-phase and one 3-phase) was collected in November 2012. The achieved removal efficiencies for the measured parameters were as follows: TS 14%, DS 6%, SS 89%, turbidity 88%, COD 15% for 2-phase OMWW, and TS 16%, DS 8%, SS 93%, turbidity 96%, COD 23% for 3-phase OMWW. Optimum removal efficiency for all tested parameters was centrifugation speed/time of 5,500 rpm (3,382 x g)/55 min for 2-phase OMWW, and 5,500 rpm (3,382 x g)/33 min for 3-phase OMWW. The removal efficiencies of the centrifugation process, especially in terms of SS, turbidity, and COD, indicate that centrifugation can be utilized in OMWW management. Furthermore, initial centrifugation could improve the efficiency of subsequent separation processes, such as membrane filtration. The results of this study will help olive oil processors add value to their co-product OMWW stream.